Method for triggering a two-stage air bag gas generator

• US 6,199,903 B1
• Filed: 04/19/1999
• Issued: 03/13/2001
• Est. Priority Date: 04/17/1998
• Status: Expired due to Fees

• Current Assignee: Daimler AG (Mercedes-Benz Group AG)
• Original Assignee: Daimler Chrysler Company LLC (Stellantis NV)
• Inventors: Brambilla, Luigi, Müller, Manfred, Rudolf, Harald
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): Hernandez, Olga
• Application Number:
  US09/293,764
• Time in Patent Office: 694 Days
• Field of Search: 701/45, 280/734, 280/735, 280/736, 280/742, 280/737, 280/728.1, 280/739, 280/732, 180/282
• US Class Current: 280/735
• CPC Class Codes: B60R 2021/0102 the monitored value being used for calculating occupant displacement
• CPC Class Codes: B60R 2021/01034 Controlling a plurality of restraint devices
• CPC Class Codes: B60R 21/01516 using force or pressure sensing means
• CPC Class Codes: B60R 21/01558 monitoring crash strength

Abstract

In a method for triggering a two-stage air bag generator in a motor vehicle, an acceleration signal is measured, processed and evaluated with respect to the accident severity according to a first evaluation process. As a function of the determined accident severity, a triggering decision is made at least for the triggering of a first stage of the gas generator. At least until a defined time period T1 has elapsed since the ignition of the first stage, the acceleration signal is evaluated according to a second evaluation process with respect to the accident severity before, on the basis of defined triggering conditions, as a function of the determined accident severity, a triggering decision is made for igniting the second stage of the gas generator.

Claims

1. A method for triggering a two-stage air bag gas generator in a motor vehicle, comprising the steps of measuring and processing an acceleration signal;

with a first evaluation process, making a triggering decision for triggering the first stage of the gas generator and

with a second evaluation process, making a triggering decision for triggering the second stage of the gas generator, and

releasing the triggering of the second stage only after elapse of a defined time period T1 since the ignition of the first stage, wherein the second evaluation process, irrespective of the initial course of the acceleration signal, at least until the defined time period T1 has elapsed since the ignition of the first stage, first the whole course of the acceleration signal is evaluated with respect to the accident severity before, on the basis of defined triggering conditions, as a function of the determined accident severity, a triggering decision is made for triggering the second stage of the gas generator.

2. The method according to claim 1, wherein the time period, T1, within a range T1min to T1max, as a function of a state variable which relates to the crash parameters and which allows a conclusion on the occurring or expected collision energy of the crash event, is changed such that the time period T1 is shifted toward the lower limit, T1min, when the state variable shows a high collision energy.

3. The method according to claim 1, wherein when a triggering decision is made for the ignition of the second stage of the gas generator, the own vehicle speed is included as a state variable, which allows a conclusion with respect to the occurring or expected collision energy of the crash event.

4. The method according to claim 3, wherein the time period, T1, within a range T1min to T1max, as a function of a state variable which relates to the crash parameters and which allows a conclusion on the occurring or expected collision energy of the crash event, is changed such that the time period T1 is shifted toward the lower limit, T1min, when the state variable shows a high collision energy.

5. The method according to claim 4, wherein at least one of the triggering conditions and the zone limits, which determine the accident severity zones, are influenced as a function of a state variable related to the occupant or as a function of a state variable related to the crash parameters, which allows a conclusion with respect to the occurring or expected collision energy of the crash event.

6. The method according to claim 5, wherein the zone limits, as a function of a state variable related to the crash parameters, which allows a conclusion with respect to the occurring or expected collision energy of the crash event, is shifted such that, as the collision energy increases, a triggering of the second stage is promoted.

7. The method according to claim 1, wherein only at the point in time, T1, or within a time interval, T1 to T1+DT, determined by a time window, DT, since the ignition of the first stage, an ignition of the second stage takes place according to the defined triggering conditions.

8. The method according to claim 7, wherein the time period, T1, within a range T1min to T1max, as a function of a state variable which relates to the crash parameters and which allows a conclusion on the occurring or expected collision energy of the crash event, is changed such that the time period T1 is shifted toward the lower limit, T1min, when the state variable shows a high collision energy.

9. The method according to claim 7, wherein at least one of the time period, T1, and the time window DT, as a function of an occupant position recognition or of a state variable for the occupant forward displacement derived from the acceleration signal, is controlled such that a triggering of the second stage is prevented when an occupant'"'"'s forward displacement has progressed too far.

10. The method according to claim 7, wherein when the time interval permitted for an ignition has elapsed and an ignition of the second stage has not taken place, the triggering conditions are changed.

11. The method according to claim 10, wherein at least one of the time period, T1, and the time window DT, as a function of an occupant position recognition or of a state variable for the occupant forward displacement derived from the acceleration signal, is controlled such that a triggering of the second stage is prevented when an occupant'"'"'s forward displacement has progressed too far.

12. The method according to claim 7, wherein when the time interval permitted for an ignition has elapsed and an ignition of the second stage has not occurred, the second stage is not ignited.

13. The method according to claim 12, wherein at least one of the time period, T1, and the time window DT, as a function of an occupant position recognition or of a state variable for the occupant forward displacement derived from the acceleration signal, is controlled such that a triggering of the second stage is prevented when an occupant'"'"'s forward displacement has progressed too far.

14. The method according to claim 1, wherein with the second evaluation process, generally the crash event is classified into a grid-type diagram of accident severity zones graduated according to the accident severity, and a necessary triggering condition for the ignition of the second stage consists of the fact that the crash event was assigned to a certain accident severity zone.

15. The method according to claim 14, wherein with the second evaluation process, the acceleration signal is processed to a DV speed signal while using an integration step, which DV speed signal is compared with time-variable zone limits and is thus assigned to an accident severity zone in a speed-event space, a necessary triggering condition for the ignition of the second stage consisting of the DV signal being situated within a defined accident severity zone.

16. The method according to claim 15, wherein the zone limits form curves in the speed-event space which are generated according to a defined function dependent on the time, and the generation of the zone limits is started by a triggering signal which is caused by a crash event.

17. The method according to claim 16, wherein the triggering signal is set by the acceleration signal when an acceleration threshold is exceeded.

18. The method according to claim 16, wherein the triggering signal is set when a restraining device is triggered which is always triggered before the ignition of the second stage, including a belt tightener, a belt force limiting device or the first stage of the gas generator.

19. The method according to claim 14, wherein at least one of the triggering conditions and the zone limits, which determine the accident severity zones, are influenced as a function of a state variable related to the occupant or as a function of a state variable related to the crash parameters, which allows a conclusion with respect to the occurring or expected collision energy of the crash event.

20. The method according to claim 19, wherein the zone limits, as a function of a state variable related to the crash parameters, which allows a conclusion with respect to the occurring or expected collision energy of the crash event, is shifted such that, as the collision energy increases, a triggering of the second stage is promoted.

21. The method according to claim 19, wherein as a function of the determined weight of the seat occupation, the zone limits are shifted such that a triggering of the second stage is provided as the weight increases.

22. The method according to claim 20, wherein as a function of the determined weight of the seat occupation, the zone limits are shifted such that a triggering of the second stage is provided as the weight increases.